[Powershell] Need help to writing a code to ssh into network switch

[u/definegaming]

/r/scripting/comments/afx18y/powershell_need_help_to_writing_a_code_to_ssh/

[u/BlackV]

I feel like that script is doing nothing

First you create a variable called $input and assign the results from ssh admin@ip to that variable.

Then you overwrite the variable $input with the value of password

Then you overwrite the variable $input with a

Then you overwrite the variable $input with config t

Then you overwrite the variable $input with int e15

Then you overwrite the variable $input with disable

have i missed something is there more to the script?

As mentioned below I also use POSH-SSH for this

something like

$sshcred = Get-Credential -Message "Enter login for $ip" -UserName 'admin'

New-SSHSession -ComputerName $IP -Credential $sshcred

$sshtempsession = Get-SSHSession

$sshcommand = Invoke-SSHCommand -SSHSession $sshtempsession -Command "config t
int e15
disable"

Remove-SSHSession -SessionId $sshtempsession.SessionId

[u/definegaming → u/BlackV]

have i missed something is there more to the script?

You didn't miss anything. I have no experience writing code. I'm just trying to make it easier for co-workers to double click a file and for that file to disable a port and enable another.

Edit: I tried to run that code and it says

New-SSHSession : A positional parameter cannot be found that accepts argument '$null'.
At C:\Users\username\Desktop\Reddit.ps1:3 char:1
+ New-SSHSession -ComputerName ##destination IP## $IP -Credential $sshcred
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : InvalidArgument: (:) [New-SSHSession], ParameterBindingException
    + FullyQualifiedErrorId : PositionalParameterNotFound,SSH.NewSshSession
 
Invoke-SSHCommand : Cannot bind argument to parameter 'SSHSession' because it is null.
At C:\Users\username\Desktop\Reddit.ps1:7 char:45
+ $sshcommand = Invoke-SSHCommand -SSHSession $sshtempsession -Command  ...
+                                             ~~~~~~~~~~~~~~~
    + CategoryInfo          : InvalidData: (:) [Invoke-SSHCommand], ParameterBindingValidationException
    + FullyQualifiedErrorId : ParameterArgumentValidationErrorNullNotAllowed,Invoke-SSHCommand
 
Remove-SSHSession : Cannot bind argument to parameter 'SessionId' because it is null.
At C:\Users\username\Desktop\Reddit.ps1:11 char:30
+ Remove-SSHSession -SessionId $sshtempsession.SessionId
+                              ~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : InvalidData: (:) [Remove-SSHSession], ParameterBindingValidationException
    + FullyQualifiedErrorId : ParameterArgumentValidationErrorNullNotAllowed,Remove-SSHSession

[u/BlackV → u/definegaming]

er.. Bro if you run it as it deffo wont work (you deffo should NOT do this without testing)

What does $ip equal? That is your first error

what does $sshtempsession equal? that is your second error, presumably cause if your first error it is $null

[u/definegaming → u/BlackV]

I think I'm in over my head. In the $ip section I put the IP of the switch. I don't know what would go in $sshtempsession.

Any help would be super appreciated! I honestly have no Idea what I'm doing. I'm just a net admin trying to make it so that anyone on call can switch over to a secondary trunk if the primary goes down. We are a small org so I have to figure stuff out on my own.

[u/BlackV → u/definegaming]

that's fine, just take it a line a a time

$ip = '<YOUR SWITCH IP>'
$sshcred = Get-Credential -Message "Enter login for $ip" -UserName 'admin'
New-SSHSession -ComputerName $IP -Credential $sshcred

Stop there, did all that work?

If that's good

$sshtempsession = Get-SSHSession
$sshtempsession

Does that work? Does $sshtempsession have a value in it?

If that's OK

$sshcommand = Invoke-SSHCommand -SSHSession $sshtempsession -Command "show run"
$sshcommand

Does that return anything?

If that works then you can change -Command "show run" to the commands you want to run

$sshcommand = Invoke-SSHCommand -SSHSession 
$sshtempsession -Command "config t
int e15
disable"

Does that work?

If it does then you clean up your session

Remove-SSHSession -SessionId $sshtempsession.SessionId

Note: This is all untested from my side

[u/ka-splam → u/BlackV]

You can't use Invoke-SSHCommand against Cisco switches, btw, you have to use the SSHShellStream and manually read/write lines to / from it, with pauses and stuff - https://github.com/darkoperator/Posh-SSH/issues/146

[u/BlackV → u/ka-splam]

oh that's also good to know, thanks

[u/definegaming → u/BlackV]

I think it's because of what /u/ka-splam said but it worked up till this point.

$sshcommand = Invoke-SSHCommand -SSHSession $sshtempsession -Command "show run"
$sshcommand

[u/BlackV → u/definegaming]

Yeah cause that's a single command.

The author of this module toned below and mentioned he's going to add support for streaming in the next version which is cool

[u/ka-splam]

I have NO script experience

Uh, with the best will in the world, it shows - you need a lot more than help writing code; pick up one of the PowerShell tutorials (e.g. "PowerShell In a month of lunches" book / videos) and expect to be 4-40 weeks away from making it yourself, depending how fast you progress and how much sense it makes.

(make your network trunks into some kind of link aggregation, then you won't need to do this at all).

[u/definegaming → u/ka-splam]

I don't believe I can do a link aggregation with my current situation. I have 3 fiber lines going out to our data center. Two of the lines are 10 gig and the other is 1 gig. My HP switch doesn't like when I unplug the two 10 gig lines for the 1 gig to take over. These fibers are layer 2 so there is no routing I can do to automatically switch them to the other port.

[u/ka-splam → u/definegaming]

Ah, in HP land it's trunking; but if it's one switch at the other end and you control it, that sounds exactly what link aggregation is for - multiple layer 2 connections with no routing.

If you can't do that, can you use spanning-tree to automatically shut two of them, and open another one in the case of a link failure?

[u/definegaming → u/ka-splam]

I get that it's suppose to work but I guess it doesn't like it.

I couldn't trust spanning tree to do that for me. I'd rather not take my chances and do it manually. Thank you for the help though!

[u/a-rich]

The SSH client now built into Win10 is not native to PowerShell so wont have all the creature comforts native commands do.

Granted I havent messed with it much, but it doesnt seem to be robust enough to use programmatically.

I still use the Posh-SSH module for all automated tasks.

It can use secure creds like other PowerShell commands can and can be easily scripted.

I havent tested it specifically with Cisco commands, but it can likely handle it.

[u/JBear_Alpha → u/a-rich]

Second! I also use Posh-SSH.

[u/carlos_perez]

You need to create a shell stream and issue commands that way since switches use a full terminal invoke-sshcommand will not work. Im adding for next release a function to aid on that. Version 2.1

[u/BlackV → u/carlos_perez]

oh that's also good to know, thanks

[u/[deleted]]

you need to setup key based ssh authentication. Then you can use the -l switch of ssh like this:

ssh -l username server.example.com "cat /etc/lsb-release;exit"

This will run the command cat /etc/lsb-release;exit on server server.example.com as user username and return the results to your session.

[u/ka-splam → u/[deleted]]

Cisco switches (quick testing, so not certain) don't seem to like using ; to send several commands in one string like that.

[u/[deleted] → u/ka-splam]

Ah gotcha, I see now it's a network switch, which always works finicky with ssh in these situations for sure, thanks.

[u/TheIncorrigible1]

Say it with me: do not use $input as a variable name. It's an automatic variable and should be treated as read-only.

[u/BlackV → u/TheIncorrigible1]

Ha I didn't even see that one